Radiographic elements,compounds and processes

ABSTRACT

A ROOMLIGHT HANDLING RADIOGRAPHIC ELEMENT OR EMULSION WHEREIN THE LIGHT-SENSITIVE LAYER OF LAYERS THEREOF ARE PROTECTED FROM EXPOSURE TO VISIBLE LIGHT; SAID ELEMENT OR EMULSION COMPRISING AN X-RAY-SENSITIVE SILVER HALIDE LAYER COMPRISING A SILVER HALIDE DESENSITIZING COMPOUND SUCH AS A NITROTHIAZOLINOTHIACYANINE AND A YELLOW DYE, AND COATED UPON SAID X-RAY-SENSITIVE LAYERS A LIGHT-AB SORBING SILVER HALIDE LAYER COMPRISING A NITROGEN-CONTAINING HETEROCYCLIC SILVER HALIDE DESENSITIZING COMPOUND AND A YELLOW DYE SUCH AS A PHENYLAZOPYRAZOL-5-ONE YELLOW DYE. PROCESSES FOR OBTAINING A RADIOGRAPHIC IMAGE EMPLOYING THE ROOMLIGHT HANDLING RADIOGRAPHIC ELEMENTS AND EMULSIONS ARE DISCLOSED. ELECTROMAGNETIC RADIATION-SENSITIVE SILVER HALIDE DE SENSITIZED WITH A NITROGHIAZOLINOTHIACYANINE OR CONTAINING A PHENYLAZOPYRAZOL-5-ONE YELLOW DYE.

June 20, 1972 c. s. DOSTES 3,571,254

RADIOGRAPHIC ELEMENTS, COMPOUNDS AND PROCESSES Filed Sept. 4, 1970LIGHT-BLOCKING SILVER HAL/0E W KEMUL S/ON LA YER J x-RAY SENS/T/VE LAYERSUPPORT /3 7k -A LIGHT SEAL/N6 BACK/N6 LAYER LIGHTBLOC/(ING SILVERHAL/0E EMULSION LAYER xRAY SENSITIVE LAYER SUPPORT X-RAY SENSITIVE LAYERLIGHT- BLOCK/N6 SILVER HAL/0E EMULSION LAYER FIG. 2

6 LA UDE 005 TE S INVENTOR.

BY w! A TTORNE Y United States Patent US. Cl. 96-101 23 Claims ABSTRACTOF THE DISCLOSURE A roomlight handling radiographic element or emulsionwherein the light-sensitive layer or layers thereof are protected fromexposure to visible light; said element or emulsion comprising anX-ray-sensitive silver halide layer comprising a silver halidedesensitizing compound such as a nitrothiazolinothiacyanine and a yellowdye, and coated upon said X-ray-sensitive layers a light-absorbingsilver halide layer comprising a nitrogen-containing heterocyclic silverhalide desensitizing compound and a yellow dye such as aphenylazopyrazol-S-one yellow dye. Processes for obtaining aradiographic image employing the roomlight handling radiographicelements and emulsions are disclosed.

Electromagnetic radiation-sensitive silver halide desensitized with anitrothiazolinothiacyanine or containing a phenylazopyrazol-S-one yellowdye.

BACKGROUND OF THE INVENTION iFlfild of the invention This inventionrelates to photographic elements and emulsions which are protected fromvisible light. In one aspect, this invention relates to photographicelements and emulsions which are desensitized toward visible light. Inanother aspect, this invention relates to photographic elements andemulsions containing a lightabsorbing yellow dye. In another aspect,this invention relates to radiographic emulsions and elements which arehighly suitable for handling and processing under conditions of ordinaryroomlight illumination without expo sure of the photosensitive layersthereof. In still another aspect, this invention relates to new yellowdyes capable of absorbing radiation of the visible spectrum. In yetanother aspect, this invention relates to new desensitizing compoundscapable of strongly depressing the lightsensitivity of silver halidewithout appreciably affecting its X-ray sensitivity. In still anotheraspect, this invention relates to the radiographic elements comprisingan X-raysensitive silver halide layer and a light-absorbing silverhalide layer, said element incorporating the new yellow dyes and the newsilver halide desensitizers.

Description of the prior art There have been various methods proposed inthe art for protecting the light-sensitive layer or layers ofphotographic elements used in obtaining X-ray photographs. Certain ofthese photographic elements have been provided with an opaque protectingmedium which is removed after exposing in a special processing bath.Such protective layers have not been entirely satifactory because thelayers are difiicult to remove after exposure to X-rays andlight-absorbing material is not always uniformly distributed throughoutthe medium. Other radio graphic elements have been prepared usingprotective outer-layers, comprising a coating of chrome-yellow, Venetianred, and the like which forms a readily removable opaque protectingmedium. This coating allows handling of the element in ordinaryroomlight but is washed off prior to development so that developmentmust of necessity be carried out in a darkroom. With any of the priorproposals for protecting the light-sensitive layer using anouter-protective opaque layer, there has also been the difficulty thatthese protective layers do not cover the edges of the film, andaccordingly, light enters the film through these edges to produceedge-fog in the light-sensitive emulsion layer. To overcome thisdifiiculty, it has been proposed to optically seal the edges of the filmby applying a black colloid edge-coating or a sealing strip of opaquepaper or fabric. It is apparent that the prior art has been unable todeduce a method for preparing a truly satisfactory roomlight handlingphotographic element. To meet the requirements of such an element, itshould be stable to visible light exposure but have substantiallyunchanged sensitivity to X-ray radiation. The element should also bestable against edge-fog without requiring special treatment or expensiveextra handling of separate film sheets to employ special opticalsealers, light-blocking cassettes, etc. The roomlight handling elementsshould also be adapted to processing in conventional processingsolutions without loss of optimum quality in the final result.

In US. Pat. 3,237,008 to Dostes and Pfaff issued Feb. 22, 1966, it isshown how to prepare a roomlight handling radiographic element whichmeets each of the above requirements while at the same time permits theoperator to watch the complete development process under ordinaryroomlight. The Dostes and Pfatf invention is accomplished by providing aradiographic element which comprises at least one X-ray-sensiti'vesilver halide layer and coated thereupon a light-absorbing silver halidelayer. Incorporated in each of the layers of the roomlight handlingradiographic element is a combination of a nitrogen-containingheterocyclic silver halide desensitizing compound capable of depressingthe light sensitivity of the silver halide without appreciably affectingthe X- ray sensitivity, and a yellow dye which absorbs a substantialportion of the visible radiation to which the silver halide issensitive, i.e., radiation between 350 and 500 m The radiographic imagesprepared from the X-ray elements of Dostes and LPfatf are of excellentquality and show good image discrimination. The silver halidedesensitizers are, however, desorbed from the silver halide grainsduring storage, especially when the temperautre rises above normal roomtemperature, thereby causing a decrease in the desensitization of thesilver halide grains to visible radiation. A second problem presented isthe lack of uniformity in the decoloration of the X-ray film duringprocessing. Normally the yellow dye used in each layer should be readilyremoved or decolorized in conventional processing solutions. However, itis found that the decoloration is not necessarily uniform and thedecoloration depends in particular upon the temperature of theprocessing baths. In any event the processing solutions are contaminatedby the yellow dyes and hence the processing lifetime of the developingsolutions are thereby greatly shortened. It should be apparent that theart would greatly benefit if a desensitizer were found which remainsabsorbed on the silver halide grains during storage thereby preventingthe decrease in the desensitization of the silver halide grains to thevisible light and allowing for greater storage life of photographicelements and if a yellow dye were known which does not dissolve in theprocessing baths, thereby not contaminating the processing solutions,and yet allow for processed radiographic elements to be clearly andunequivocably observable.

SUMMARY OF THE INVENTION In accordance with this invention, there areprovided novel photographic silver halide emulsions desensitized to 3visible electromagnetic radiations. There is provided further,photographic silver halide emulsions containing a novel light-absorbingyellow dye.

In a preferred embodiment of this invention, there are provided novelroomlight handling radiographic elements which do not show an increasein sensitivity to visible radiation during storage or increase intemperature, and which do not contaminate the processing baths duringdevelopment but remain permanently and uniformly colored therebyallowing clear observation of the radiographic image. The improvementsof the present invention are obtained by incorporating in an outeremulsion light-absorbing layer and in the inner-most light sensitive,X-ray sensitive emulsion layer a yellow dye which does not dissolve inthe processing baths, and by incorporating in said inner emulsion layera new desensitizer against visible light.

It is therefore an object of the present invention to provide a newyellow dye which will not dissolve in photographic processing solutions.A further object is to provide new silver halide desensitizingcompounds. A further object is to provide a new silver halidedesensitizing compound Which is capable of strongly depressing the lightsensitivity of silver halide without appreciably affecting the X-raysensitivity of the silver halide grains. It is yet a further object toprovide useful silver halide desensitizing compounds which stronglyadhere to the silver halide grains. A still further object of thepresent invention is to provide a photographic element for X-rays whichcan be handled under conditions of ordinary roomlight illumination.Still a further object is to provide roomlight handling radiographicelements which are stable against edge-fog. A still further object is toprovide radiographic elements which upon exposure can be processed inroomlight using conventional processing solutions. Another object is toprovide roomlight handling radiographic elements which havelight-absorbing outer protective layers which permit observation ofimage development under ordinary roomlight conditions. Another and stillfurther object is to provide radiographic elements whose sensitivity tolight does not increase during its shelf life. Other objects of thisinvention will become obvious to those skilled in the art from thatwhich appears hereafter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the presentinvention, it has been found that photographic emulsions comprising ahydrophilic colloid and electromagnetic radiation-sensitive silverhalide layer can be strongly desensitized to visible radiations byincorporating a new silver halide desensitizer into said emulsion. Inanother embodiment of the invention, it has been found thatlight-blocking photographic emulsion and elements which do notcontaminate processing solutions can be provided by incorporating anovel light-absorbing yellow dye in said emulsion. In another embodimentof this invention, it has been found that without modifying thestructure of the radiographic element as disclosed in theaforementiioned Dostes et al. patent, a superior prodnot can be obtainedby incorporating a new silver halide desensitizer and a new filter dyeinto a radiographic element comprising an outer light-absorbing layerand an inner light-sensitive, X-ray-sensitive emulsion layer. The newdesensitizing compound is capable of greatly depressing the lightsensitivity of the silver halide without appreciably affecting the X-raysensitivity of said silver halide. Among the unexpected and unobviousproperties of the new desensitizer is the fact that the new desensitizerremains adsorbed on the silver halide grains thereby ensuring a longershelf life and a greater stability as compared with the prior artroomlight handling elements. The added stability of theroomlight-handling radiographic element is accomplished withoutaffecting the removability of the desensitized silver halide grains fromthe layers of the radiographic elements in conventional processingbaths. The

4 new desensitizer is used only in the inner X-ray sensitive layers,whereas the desensitizers of the aforementioned Dostes et al. patent areemployed in the overcoat in view of their ability to migrate rapidlyinto the baths during the processing operation. The yellow dye, whichfunctions as a filter which absorbs visible light, is not readilyremoved from the emulsion layers. Upon processing the element, oneobtains a radiogram having a black image upon a uniform yellowbackground.

By reference to the accompanying drawing, there can be seen the mannerin which the roomlight handling radiographic elements of the inventioncan be prepared. FIG. 1 shows a sectional view of a photographic elementhaving a light-sealing backing layer, whereas FIG. 2 shows an elementwhich has an X-ray sensitive layer and a light-absorbing layer on eachside of the single support.

The new desensitizing compounds which are employed in the practice ofthe invention are 3-al-kyl-3'-alkyl nitrothiazolinothiacyanine halides.Suitable compounds can be represented by the structure wherein X ishalide such as chloride, bromine, or iodine and R and R each are analkyl group, for example, methyl, ethyl, propyl, butyl and the like.Examples of preferred nitrothiazolinothiacyanines are:

3-methyl-3-methyl-6-nitrothiazolinothiacyanine iodide3-ethyl-3'-ethyl-6-nitrothiazolinothiacyanine iodide3-ethyl-3'-methyl-6'-nitrothiazolinothiacyanine iodide3-butyl-3-butyl-6'-nitrothiazolinothiacyanine chloride3-ethyl-3'-ethyl-5'-nitrothiazolinothiacyanine iodide 3 -ethyl-3-methyl-5 '-nitrothiazolinothiacyanine chloride3-methyl-3'-methyl-6'-nitrothiazolinothiacyanine iodide and3-butyl-3'-butyl-5'-nitrothiazolinothiacyanine chloride.

The new desensitizers of the present invention are conveniently preparedby methods referred to in, The Cyanine Dyes and Related Compounds by F.M. Hamer, Interscience Publishers, New York 1964, page 728. Thepreparation of 3 ethyl 3' methyl 6 nitrothiazolinothiacyanine is, forexample, readily accomplished by reacting the methyl sulfate of2-methylmercapto-3-methyl- 6-nitrobenzothiazolium with the 2methylthiazolinium ethyl paratoluene sulfonate.

The new yellow dyes which are employed in the practice of the inventionare sulfophenyl phenylazopyrazol-S-ones having the structure:

wherein each of R and R is hydrogen, an alkyl group, such as methyl,butyl, amyl, hexyl and the like or alkoxy group such as methoxy, butoxy,amyloxy, hexoxy and the like, at least one of R or R is an alkyl oralkoxy group; R is an alkyl or alkoxy group such as methyl, ethyl,propyl, butyl, and the like or methoxy, ethoxy, propoxy and the like; Mis hydrogen, an alkali metal such as K, Na and the like, ammonium orsubstituted ammonium; and m and n are each equal to zero or one, atleast one of m or n being equal to one. Illustrative of preferredfilter-dyes which may be used in this invention are those wherein R andR can each be hydrogen or have from 4 to about 12 carbon atoms, at leastone of R and R having from 4 to about 12 carbon atoms; R has 1 to 4carbon atoms, and R R and 40 M are in the ortho or para position.Another preferred group of filter-dyes are those wherein R and R eachare hydrogen or an alkyl or alkoxy group having from 4 to -6 carbonatoms, at least one of R and R being alkyl or alkoxy. Another preferredgroup of filter-dyes are those wherein each of R and R are hydrogen orhave 5 or 6 carbon atoms at least one of R or R being an alkyl or alkoxygroup. Still another preferred group of filter-dyes are those wherein Ris an alkoxy group of 5 or 6 carbon atoms, R is hydrogen, m is equal tozero and R and SO M are in the para position. Illustrative of thecompounds useful in this invention are:

1-p-sulfophenyl-3-methyl-4-p-i-amyloxyphenylazopyrazol-S-one, sodiumsalt l-p-sulfophenyl-3-methyl-4-p-n-arnyloxyphenylazopyrazol-S-one,sodium salt 1-p-sulf0phenyl-3-methyl-4-p-n-hexoxyphenylazopyrazol-S-one,sodium salt l-p-sulfophenyl-3-methyl-4-p-n-butoxyphenylazopyrazol-S-one,sodium salt l-p-sulfophenyl-3-pr0pyl-4-o-n-butylpheny1-azopyrazol-S-one, ammonium salt The filter dyes are convenientlyprepared by a threestep reaction, for example, the sodium salt ofl-p-sulfophenyl 3 methyl 4 p n amyloxyphenylazopyrazolone-S is obtainedaccording to the following equation:

CHaC OzNa I some 6 out-(choke -N=N [crn 011300211 The visible-lightabsorbing dyes which are used with the desensitizing compounds in thesilver halide layers should advantageously be dyes which are stable in acolloid carrier and should advantageously be nondifiusing. Suitable dyesshould also be highly absorbent in regions of the spectrum to which thesilver halide is sensitive, i.e. 350-500 mg, but should transmit theremainder of the visible spectrum freely so that it is possible toobserve the progress of development under ordinary roomlight. The mostuseful dyes are soluble in photographic gelatin and insoluble in theprocessing solutions.

According to the invention, the new desensitizers when employed inroomlight handling radiographic elements, are incorporated only in theinnermost X-raysensitive silver halide layer or layers. In the outerlightabsorbing layers, there is employed nitrogen-containingheterocyclic desensitizers of US. Pat. 3,237,008. The compounds whichare useful in the practice of the invention are represented by thefollowing structural formula:

Z-methyl-S-nitrobenzothiazole metho-p-toluenesulfonate4-nitro-6-chlorobenzotriazole 6-ethoxy-2-(m-nitrostyryl) quinoliniumethlethosulfate NHz NH:

3,7-diamino-5-phenyl-phenazinium chloride S-nitrobenzimidazole OzNAdditional useful nitrogen-containing heterocycles representative of theabove classes comprise the following:

2-(o-nitrostyryl)-3-ethylbenzothiazolium iodide, 2- (o,p-dinitrostyryl)-benzothiazole, 6-nitro-benzo-l,2,3-triazole,4-chloro-benzo-1,2,3-triazole, S-chloro-benzo-1,2,3-triazole,2-methyl-6-nitrobenzothiazole metho-p-toluene sulfonate,2-(p-nitrostyryD-quinoline metho-p-toluenesulfonate,4-(p-nitrostyryl)-quinoline methoiodide, 1-ethyl-7-nitro-quinoliniumethylsulfate, 1,3-diamino-5-methylphenazinium chloride,1,3-diamino-S-benzylphenazinium chloride,3,7-diamino-SB-hydroxy-ethylphenazium chloride, 5-chlorobenzimidazole,Z-methyl-S-chlorobenzimidazole, Z-mercaptobenzimidazole,Z-mercapto-6-chlorobenzimidazole.

The desensitizing compounds of the above type which can beadvantageously employed in the practicing of our invention have beendescribed in one or more of the following representative US. patents:2,400,872 issued May 28, 1946; 2,541,472 issued Feb. 13, 1951; 2,939,789issued June 7, 1960; 2,915,395 issued Dec. 1, 1959; and 2,066,099 issuedDec. 29, 1936.

In accordance with this invention the new desensitizing compounds can beemployed in the inner-most layer, which is X-ray sensitive and alsolight sensitive, at a concentration in the order of from about mg. to500 mg. per mole of silver halide. At the higher concentrations, thesilver halides of the X-ray-sensitive layer are desensitized not only tovisible light but in part also to X-rays, whereas at the lowerconcentrations, the loss of sensitivity to X-rays is negligible. Whenemployed in non-radiographic elements, the concentration is not limitedsince there is no concern as to desensitizing X-ray-sensitive silverhalides. The light-absorbing dye is added to the gelatin inconcentrations in the order from about 0.5 g. to about 100 g. per 150 g.of dry gelatin. The silver concentration in the innermost layer can varyLirom about 400 mg. to about 1 g. of silver per square oot.

The outer-light-absorbing protective layer normally comprises a silverhalide emulsion layer more strongly desensitized than in the inner-mostlight-sensitive layer. In the outer-most layer, in accordance with theinvention, an eXcess of desensitizing compound is employed in comparisonto the concentration of desensitizing compound in the inner-most layer.The concentration of desensitizer in the outer-light-absorbingprotective layer can be in the order of from about 20 mg. to 5.0 g. permole of silver halide or more depending upon the extent ofdesensitization desired and upon the desensitizing compound employed.The visible light-absorbing dye is added in combination with thedesensitizing compound in the emulsion in an amount of from about 0.5 g.to about 100 g. per 150 g. of dry gelatin. In the outer-light-absorbingemulsion layer a suitable concentration of sliver per square foot canvary from about 100 to about 900 mg. of silver per square foot.

The outer-light protecting emulsion layer can comprise a silver halideemulsion which forms latent images predominantly inside the silverhalide crystal, such as those described in Davy and Knott, US. Pat.2,592,250 issued Apr. 8, 1952. Where emulsions of this type are usedaccording to the invention desensitizing compounds of the type hereindescribed are incorporated in an amount in the range from about 25 mg.to about 250 mg. per mole of silver halide. In such emulsion layers thelightabsorbing dyes are contained in combination with desensitizingcompounds in the range as indicated above for outer-light-absorbinglayers.

Silver halide emulsions which form latent images predominantly insidethe silver halide crystal are also referred to as internal imageemulsions and have been described in Luckey et al., US. Pat. 2,996,382issued on Aug. 15, 1961. The internal image emulsions which are usefulaccording to our invention have little or no surface sensitivity. Suchinternal image emulsions, when measured according to normal photographictechniques by coating a test portion of the emulsion on a transparentsupport, exposing to a light-intensity scale having a fixed time between0.01 and 1 second, bleaching 5 minutes in a 0.3 percent potassiumferricyanide solution at 65 F., and developing for about 5 minutes at 65F. in developer B below, has a sensitivity, measured at a a density of0.1 above fog, appreciably greater (e.g., at least 1.4 log greater) thanthe sensitivity of an identical test portion which has been exposed inthe same way and developed for 6 minutes at 68 F. in developer A below.

The developer compositions which are used in defining an internal imageemulsion by comparison with a conventional surface image emulsiondeveloper, compositions A and B are given hereinafter. Developer A isthe usual type of surface image developer and developer B is an internaldeveloper having high silver halide solvent activity.

The following developer compositions are used in the method ofdetermining relative internal sensitivity of preferred emulsions:

Grams N-methyl-p-aminophenol sulfate 0.31 Sodium sulfite, desiccated39.6 Hydroquinone 6.0 Sodium carbonate, desiccated 18.7 Potassiumbromide 0.86 Citric acid 0.68 Potassium metabisulfite 1.5 Water to make1.0 liter.

Grams N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide5.0 Sodium thiosulfate 10.0

Water to make 1.0 liter.

Suitable internal image emulsion are described in Davey and Knott, US.Pat. 2,592,250 issued Apr. 8, 1952. Other emulsions which can be used inthe outermost layers of the present invention comprise, for example,relatively insensitive silver chlorobromide and silver bromoiodideemulsions.

The methods of incorporating the desensitizing compounds and visiblelight-absorbing materials in silver halide emulsions are well known tothose skilled in the art. The desensitizing compounds can be directlydispersed in the emulsions, or they can be dissolved in water (or inorganic solvents, such as methanol, ethanol, etc., where the'water-solubility is not sufiiciently great) and added in the form oftheir solutions. While the visible light-absorbing dyes can be directlydispersed in the emulsions, it is convenient to add the same in the formof solutions in appropriate solvents. Methanol, ethanol, pyridine, andthe like have proved satisfactory. Mixtures of sol-vents, e.g., pyridinediluted with methanol or acetone, can also be used. According to theinvention the desensitizing compounds and the visible light-absorbingdye are dispersed in the finished emulsions and should be uniformlydistributed throughout the emulsion. The following procedure issatisfactory:

Stock solutions of the desensitizing compounds and visiblelight-absorbing dye are prepared by dissolving the same in appropriatesolvents as described above. The desired amount of stock solution of thedye (or desensitizing compounds) is slowly added to the liquidgelatino-silver halide emulsion with stirring. Stirring is continueduntil the dye is thoroughly incorporated in the emulsion. Then thedeisred amount of the stock solution of the desensitizing compound (ordye, if the desensitizing compound has been added first) is slowly addedto the emulsion, while stirring. Stirring is continued until the secondsolution is thoroughly incorporated. The treated emulsion can then becoated out on a suitable support, such as glass, cellulose derivativefilm, resin film, or paper, to suitable thicknesses and allowed to dry.Most usually the roomlight handling radiographic elements of ourinvention are duplicoated, i.e., coated on either side of a support withthe light-sensitive, X-raysensitive emulsion layer being the innermostlayer, and the light protecting outer layer being coated as a secondlayer on either side of the support. The details of such coating methodsare well known to those skilled in the art and have been described inUS. Pat. 1,947,160 issued Feb. 13, 1934.

The coating thickness of the innermost light-sensitive, X-ray-sensitivelayer of the multilayer radiographic elements prepared according to theinvention can vary widely, but in general, thicknesses from about 0.4 toabout 1.2 units, can be used. The thicknesses of the outer-protectivelayers are not critical and can depend more upon the concentration ofthe light diffusing, e.g. silver halide, and absorbing materials persquare foot of coated surface.

This invention can be further illustrated by the following examples ofpreferred embodiments thereof, although it will be understood that theseexamples are included merely for illustrating this invention.

EXAMPLE I To a high contrast course-grained silver bromoiodide gelatinemulsion having a low iodide content of the type normally used inradiography and containing 150 gm. of dry gelatin per mole of silverhalide is added 150 mg. of3'-methyl-3-ethyl-6'-nitrothiazolinothiacyanine iodide per mole ofsilver halide and 3 g. of 1-p-sulfophenyl-3-methyl4-p-hexoxyphenylazopyrazol-5-one sodium salt per 150 g. of dry gelatin.The emulsion is coated at 90 F. on both sides of a cellulose triacetatebase to obtain a coverage of 900 mg. silver per square foot on eachside.

Over each of the emulsion layers is applied a layer of non-chemicallysensitized fine-grain bromoiodide gelatin emulsion incorporating therein1 g. of 4-nitro-6-chlorobenzotriazole per mole of silver halide and 30g. of l-p-sulfophenyl-3-methyl-4-p-n-hexoxyphenylazopyrazole-S-oue for150 g. of dry gelatin. The overcoat is coated at a coverage of 104 mg.of silver per square foot per side. A11 antiabrasion layer is thencoated over the light-absorbing emulsion layer and the element is dried.

The resulting film is exposed to an 80 kv. X-ray source under roomlightillumination, developed for 5 minutes at 20 C., fixed and washed. All ofthe steps for processing the roomlight handling radiographic element ofthis example are carried out under both inactinic safe lightillumination and 50 lux artificial light illumination.

A control sample is prepared which is identical to the above preparedfilm, except said control sample does not contain any desensitizer,filter dye or absorbing overcoat. The control sample is exposed anddeveloped in the same manner as the new film.

The radiogram obtained from the new film produced by this example is ofgood quality and does not show 10 evidence of edge fog. The results forthe new film and the control sample are summarized in Table I.

A conventional cellulose acetate film base is coated with a typicalcoarse-grain silver bromoiodide gelatin X-ray sensitive emulsion whichis desensitized with 43.5 ml. of 4-nitro-6-chlorobenzotriazole(I) and towhich is added 25 g. of 3-carboxy-l-(1'-sulfophenyl)-4-(4'-sulfopheny1-azo)-5 pyrazolonedisodium salt (II) per mole of silver halide. Thesilver content of the coating is 882 mg. per square foot. As anouter-light-absorbing layer a fine-grain, silver bromoiodide gelatinemulsion strongly desensitized with 900 mg. of compound (I) andcontaining g. of compound (II) per mole of silver halide is coated overeach of the light-sensitive, -X-ray-sensitive layers at a thickness togive 540 mg. of silver per square foot. This film, identified in TableII as A, is typical of the X-ray films disclosed in US. Pat. 3,237,008.

A film, identified as Film B in Table II, is prepared in the manner ofExample 1.

After drying, the coated films are cut into strips and stored. Uponremoval from storage, the film strips are exposed to a tungsten lamp of400 watts, at 2,850 K. for seconds, at a distance of 75 cm. anddeveloped at 20 C., for 5 minutes and fixed in a conventional fixingbath. The results are summarized in Table II.

TAB LE II Desensitization to visible light (Log E) Fog after storageperiod (month) 12 months X-ray film of storage 0 3 6 9 12 EXAMPLE IIITABLE III Inaotinie light 50 lux artificial light X-ray film Speed GammaFog Speed Ganuna Fog Control 100 4.6 0.02 Black 74 New film 100 4.5 0.03100 4.4 0.05

EXAMPLE IV This example illustrates the manner of preparation of ayellow dye of the invention.

In a flask of one liter equipped with a mechanical agitator and a refluxcondenser there is introduced 55.6 g. of para nitrophenyl, 55.2 g. ofthe anhydrous potassium carbonate 66.0 g. of hexylbromide and 400 ml. ofanhydrous acetone and heated under reflux for about 96 hours. Thesolvent is removed under vacuum and 400 ml. of water are added. Thesolution is extracted 2 times with 200 ml. respectively of benzene. Thebenzene extracts are combined and washed 3 times with 200 ml. of asolution of 10% sodium hydroxide. Benzene is heated and the remainingoil is distilled under vacuum.

Sixty-seven (67 g.) grams of the obtained para-n-hexoxynitrobenzene ismixed with 100 ml. of methanol in the presence of 2 g. of Raney Nickeland catalytically reduced at 50 C. under 22 lbs. of pressure for 1 hour.Upon filtering and heating the solvent under vacuum and distilling, oneobtains as the residue para n-hexoxyaniline.

In a one-liter flask sitting in a cooling medium, supplied withmechanical agitator, a thermometer and a dropping funnel there isintroduced 57.9 g. of p-n-hexoxyaniline, 300 ml. of water and 75 ml. ofconcentrated hydrochloric acid. To the above solution, over a period offrom 50 to about 60 minutes 21 g. of sodium nitrite in 30 ml. of wateris introduced very slowly while continuously maintaining the temperaturebelow C. Upon completing the introduction of the sodium nitrite, thesolution is agitated for 30 minutes. Into a two-liter flask equippedwith a mechanical agitator and a thermometer 76.2 g. ofp-sulfophenylmethylpyrazalone is dissolved in a solution of sodiumhydroxide. To the solution is added 90 g. of sodium acetate. Thediazonium prepared and obtained in the above step is then introducedwhile maintaining the mixture at a temperature from 0 to C. A yellowcolored product falls out immmediately.

The mixture is cooled and agitated for 2 hours. The dye, which is likegum, is filtered while still wet and put in 400 ml. of acetic acid. Themixture is heated to boiling then cooled and filtered. The dye isre-crystallized in acetic acid and dried under vacuum at a temperatureof about 40 C. to about 50 C. One hundred seventy-three grams 173 g.) ofthe yellow dye was obtained with a yield of 69.5%.

The dye is in a form of an orange powder and melts and decomposes atabout 250 C. The molecular co-eflicient of adsorption in water shows anepsilon of 22.200 with a maximum of absorption at 416-419 m EXAMPLE VThis example describes the typical method for the preparation of thedesensitizers. In a 6-liter 3-necked flask there is introduced 3 litersof anhydrous pyridine, 1.060 kg. of methyl sulfate of 3-methyl-2-methylmercapto-6-nitrobenzothiazolium and .905 kg. of ethyl paratoluene'sulfonate of Z-methyl-thiazolienium. The mixture is stirred and heatedat 100 for about 20 minutes and then cooled to 0 whereupon a dyecrystallizes out. The mixture is filtered. The solid is suspended in 3liters of ethanol and refluxed. It is then added a solution of 675 g. ofsodium iodide dissolved in 3 liters. of triethanolamine, agitated for 30minutes, filtered and heated in warm alco- 1101. One obtains 730 g. of3-ethyl-3'-methyl-6-nitrothiazolinothiacyanineiodide.

The invention can be further described by reference to the accompanyingdrawing. In FIG. 1 the support is coated with a light-sensitive,X-ray-sensitive layer 11 which has coated thereon a light-absorbingsilver halide emulsion layer 12 which prevents the exposure of thelight-sensitive layer 11 during roomlight handling of the radiographicelement. On the back side of the element, there is coated alight-sealing backing layer 13. The backing layer suitably employed inthe invention must be an antihalation layers which dissolves smoothly inphotographic developers and which do not disintegrate and contaminateconventional developer solutions, such as described in U.S. Pat.2,327,828 issued Aug. 24, 1943.

In FIG. 2 of the accompanying drawing the support is coated on each sidewith an X-ray-sen'sitive, light-sensitive layer 11 and superimposed oneach of the lightsensitive layers are the light-absorbing silver halideemulsion layers 12. In roomlight handling element of the types shown inFIG. 2, a light-sealing backing layer is not used since the outerprotective layers protect the inner-most layer 11 from visible lightexposure.

The X-ray film of my invention is particularly useful in dentistry andin industrial radiography.

Any of the useful photographic addenda may be incorporated intoX-ray-sensitive emulsion layer.

As indicated, heretofore, the X.-ray-sensitive emulsion layers arecoated upon a support. Typical film supports are cellulose nitrate,cellulose ester, polyvinyl acetal, polystyrene, polyethylene,terephthalate, other polyesters, and the like. Supports such as cards orpaper which are coated with alphaolefin polymers, particularly polymersof alpha-olefins containing 2 or more carbon atoms, as exemplified bypolyethylene, polypropylene, ethylene-butene co-polymers, and the like,give good results.

The thickness of said support can vary as well known in the art in orderto practice eifectively my invention.

The silver halide emulsions used with this invention can comprise silverchloride, silver bromide, silver bromoiodide, silver chlorobromoiodideor mixtures thereof. The emulsions may be coarse or fine grain and canbe prepared by any of the well-known procedures, eg single jetemulsions, double jet emulsions, such as Lippman emulsions, ammoniacalemulsions, thiocyanate or thioether ripened emulsions such as thosedescribed in Nietz et al., U.S. Pat. 2,222,264 issued Nov. 4, 1940;Illingsworth U. S. Pat. 3,320,069 issued May 15, 1967; and McBride U.S.Pat. 3,271,157 issued Sept. 6, 1966. Surface image emulsions may be usedor internal image emulsions such as those described in Davey et al. U.S.Pat. 2,592,250 issued Apr. 8, 1952. The emulsions may be regular grainemulsions such as the type described in Klein and Moisar, I. Phot. Sci.,vol. 12, No. 5, Sept/Oct, 1964, pp. 242- 251. With respect to theX-ray-sensitive layers particularly good results are obtained withgelatino silver bromoiodide emulsions in which the average grain size ofthe silver bromoiodide crystal is in the range of about 0.5 to about 5microns.

The X-ray-sensitive emulsions described herein can be chemicallysensitized with compounds of the sulfur group, noble metal salts such asgold salts, reduction-sensitized with reducing agents, and combinationsof these. Furthermore, the X-ray-sensitive emulsion layers can behardened with any suitable hardener or combination such as aldehydehardeners, aziridine hardeners, hardeners which are derivatives ofdioxane, vinyl sulf-ones, oxypolysaccharides, such as oxystarch, oxyplant gums, inorganic hardeners such as chromium salts, and the like.

The silver halide coatings of the radiographic and other elements usefulin this invention can contain any of the hydrophilic, water-permeablebinding materials suitable for this purpose. Suitable materials includegelatin, colloidal albumen, polyvinyl compounds, cellulose derivatives,acryl amide polymers and the like, alone or in combination and mixtures.The binding agents for the emulsion layer of the radiographic and otherphotographic elements can also contain dispersed polymerized vinylcompounds. Certain of these compounds are disclosed, for example, inU.S. Pats. 3,142,568 of Nottorf issued July 28, 1964; 3,193,386 of Whiteissued July 6, 1965; 3,062,672 of Houck et a1. issued Nov. 6, 1962; and3,220,844 of Houck et a1. issued Nov. 30, 1965; and include thewater-insoluble polymers and latex co-polymers of alkyl acrylates andmethacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, orthe like.

The X-ray-sensitive radiographic silver halide coatings and otherphotographic silver halide coatings can also contain additionaladditives, particularly those known to be beneficial in photographicemulsions. For example, they can contain speed-increasing compounds, forexample, onium salt, such as quaternary ammonium ternary sulfoniumsalts, polyalkylene glycols, thioethers and the like. The photographicsilver halide coatings can be stabilized with mercury compounds,azindenes quaternary benzothiazolium compounds, hydroxy substitutedaromatic compounds, and the like.

The photographic silver halide emulsions or coatings used in myinvention can also contain non-ionic, anionic and/ or amphoteric coatingaids. Some useful coating aids 13 include, for example, saponin, alkylsubstituted aryl ox alkylene ethyl sulfonates of the type described inUS. Pat. 2,600,831 issued June 17, 1952, maleopimarates of the typedescribed in US. Pat. 2,823,123 issued Feb. 11, 1958, taurinederivatives of the type described in US. Pat. 2,739,891 issued on Mar.27, 1956, and alkyl aminopropionates of the type described in U.S. Pat.3,113,816 issued May 19, 1964. Typical of still other good coating aidsand surfactants which can be employed in the emulsions used with thescreens of this invention include the alkylphenoxy poly(hydroxyalkyleneoxides) such as alkylphenoxy poly(glycidols) having from about to about12 glycidol units, for example, such as those disclosed in British Pat.1,022,878 issued Mar. 16, 1966, to Olin Mathieson. The emulsions andradiographic combinations used and described herein can containincorporated developing agents such as polyhydroxy benzenes,aminophenols and 1,3-pyrazolidones.

The radiographic silver halide emulsions and other photographicemulsions can contain various protective overcoats such as those whichcomprise colloidal silica in an overcoat comprising gelatin and at leastone other hydrophilic colloid, including gelatin-compatible acrylicpolymers which improve various physical characteristics and opticalclarity.

This invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be etfected within the spirit and scope of theinvention.

I claim:

1. In a photographic element comprising a support having coated thereonat least one X-ray sensitive gelatinosilver halide emulsion layercomprising a silver halide desensitizing compound and a yellow dye, andcoated on said X-ray-sensitive layer at least one light-absorbinggelatino-silver halide emulsion layer comprising a nitrogencontainingheterocyclic silver halide desensitizing compound distinct from saiddesensitizing compoud in the X- ray-sensitive silver halide emulsionlayer, and a yellow dye, said yellow dye being absorbent in the regionsof the visible spectrum in which said gelatino-silver halide emulsion issensitive and capable of transmitting the remainder of the visiblespectrum, the improvement wherein said desensitizer contained in theX-ray-sensitive silver halide emulsion is a 3-alkyl-3 alkyl 6'nitrothiazolinothia cyanine present in desensitizing concentration andsaid yellow dye, present in visible-light absorbing concentration, is acompound having the structural formula wherein each R and R is hydrogen,an alkyl or alkoxy group of from about 4 to about 12 carbon atoms withthe condition that at least one of R or R is an alkyl or an alkoxygroup; R is an alkyl or alkoxy group of from 1 to about 4 carbon atoms;M is hydrogen, an alkali metal, ammonium, or substituted ammonium; and mand n are equal to zero or one with the condition that at least one of mor n be equal to one.

2. In a photographic element as in claim 1 wherein said desensitizercontained in the X-ray-sensitive silver halide emulsion layer is presentin a range of from about 0.02 g. to about 0.5 g. per mole of silver,said densensitizer present in the light-absorbing gelatino-silver halideemulsion layer is present in a range of from about 20 mg. to about 5 g.per mole of silver and said yellow dye is present R a lm 14 in eachlayer in a range of from about 0.5 g. to about g. per g. of dry gelatin.

3. In a photographic element as in claim 1 wherein the support is coatedon both sides with said X-ray-sensitive gelatino-silver halide emulsionlayers, said emulsion layers having thereon, said light-absorbinggelatino-silver halide emulsions.

4. In a photographic element as in claim 1 wherein saidnitrogen-containing heterocyclic compound is 4-nitro-6-chlorobenzotriazole.

5. In a photographic element as in claim 1 wherein R R and each SO Mgroup are in the ortho or para position.

6. In a photographic element as in claim 1 wherein each of R and R ishydrogen or an alkoxy or alkyl group having from 4 to 6 carbon atoms.

7. In a photographic element as in claim 1 wherein each of R and R ishydrogen or an alkoxy or alkyl group having 5 or 6 carbon atoms.

8. In a photographic element as in claim 7 wherein R is an alkoxy groupin the para position, R is hydrogen and m equals zero.

9. In a photographic element as in claim 1 wherein R is an alkoxy groupin the para position, R is hydrogen, in equals zero, and SO M is in thepara position.

10. In a photographic element as in claim 1 wherein said light-absorbingsilver halide layer comprises silver halide which forms latent imagespredominantly inside the silver halide crystals.

11. In a photographic element as in claim 10 wherein saidnitrogen-containing heterocyclic silver halide desensitizing compound ispresent in the light-absorbing silver halide layer in a range of fromabout 25 mg. to about 250 mg. per mole of silver halide.

12. In a photographic element as in claim 1 wherein said desensitizer inthe X-ray-sensitive layer is 3-ethyl-3'- methyl 6'nitrothiazolinothiacyanine halide, said nitrogen-containing heterocycliccompound in the light-absorbing layer is 4-nitro-6-chlorobenzotriazoleand said yellow dye is 1 p sulfophenyl 3 methyl 4 p nhexoxyphenylazopyrazol-S-one, sodium salt.

13. In a photographic elements as in claim 12 wherein saidlight-absorbing layer comprises silver halide which forms latent imagespredominantly inside the silver halide crystals.

14. X-ray-sensitive gelatino-silver halide emulsion comprising a3-alkyl-3'-alkyl-6'-nitrothiazolinothiacyanine iodide in a desensitizingconcentration and a dye in visiblelight absorbing concentration havingthe structural formula:

NN R

wherein each of R and R is hydrogen, an alkyl or alkoxy group of fromabout 4 to about 12 carbon atoms with the condition that at least one ofR or R is an alkyl or an alkoxy group; R is an alkyl group or alkoxygroup of from 1 to 4 carbon atoms; M is hydrogen, an alkali metal,ammonium or substituted ammonium; and m and n are each equal to zero orone with the condition that at least one of m or n be equal to one.

15. An X-ray-sensitive gelatino-silver halide emulsion as in claim 14wherein said 3-alkyl and 3-alkyl groups can have from 1 to 8 carbonatoms and each of R and R have from 4 to 6 carbon atoms and are in theortho or para position.

16. An X-ray-sensitive gelatino-silver halide emulsion as in claim 14wherein said 3-alkyl and 3'-alkyl groups have from 1 to 3 carbon atomsand each of R and R is hydrogen or an alkoxy or alkyl group having 5 or6 carbon atoms.

17. An X-ray-sensitive gelatino-silver halide emulsion as in claim 14wherein each of R and R is hydrogen or an alkoxy group.

18. An X-ray-sensitive gelatino-silver halide emulsion as in claim 17wherein R has 5 or 6 carbon atoms and is in the para position, R ishydrogen, in equals zero and -SO M is in the para position.

19. An X-ray-sensitive gelatino-silver halide emulsion comprising 3ethyl 3' methyl 6 nitrothiazolinothiacyanine iodide in a desensitizingconcentration and 1 p sulfophenyl 3 methyl 4 p nhexoxyphenylazopyrazol-S-one, sodium salt in visible light absorbingconcentration.

20. In a process for producing a radiographic image, said processcomprising (a) exposing in room light a roomlight handling radiographicelement, and (b) developing said element in roomlight in a radiographicsilver halide developing solution, the improvement wherein said elementcomprises an X-ray-sensitive silver halide emulsion of claim 14.

21. In a photographic emulsion comprising a hydrophilic colloid, atleast one electromagnetic radiationsensitive silver halide and adesensitizer to visible radiation, the improvement wherein saiddesensitizer is a 3- alkyl-3'-alkyl-6-nitrothiazolinothiacyanine halide.

22. A photographic emulsion as in claim 21 addition ally comprising ayellow dye having the structural formula SM)m wherein each R and R ishydrogen, an alkyl or alkoxy group of from about 4 to about 12 carbonatoms with the condition that at least one of R or R is an alkyl or analkoxy group; R is an alkyl or alkoxy group of from 1 to about 4 carbonatoms; M is hydrogen, an alkali metal, ammonium, or substitutedammonium; and m and n are each equal to zero or one with the conditionthat at least one of m or n be equal to one.

23. In a photographic emulsion comprising a hydrophilic colloid, atleast one electromagnetic radiation sensitive silver halide and a yellowdye, the improvement wherein said yellow dye is represented by thestructural formula 3M in a )n- 2 wherein each R and R is hydrogen, analkyl or alkoxy group of from about 4 to about 12 carbon atoms with thecondition that at least one of R or R is an alkyl or alkoxy group; R isan alkyl or alkoxy group of from 1 to about 4 carbon atoms; M ishydrogen, an alkali metal, ammonium or substituted ammonium; and m and nare each equal to zero or one wth the condition that at least one of mor n be equal to one.

References Cited UNITED STATES PATENTS 3,237,008 2/1966 Dostes et a1.96101 3,282,699 11/1966 Jones et al. 9684 3,148,187 9/1964 Heseltine9684 NORMAN G. TORCHIN, Primary Examiner R. FIGHTER, Assistant ExaminerUS. Cl. X.R. 9684

